1. Field of the Invention
The present invention relates to a fluid flow meter, and in particular to the type of flow meter in which the fluid flow is directed to a movable member and displacement of the movable member is transformed into an electrical signal.
2. Description of the Prior Art
One conventional flow meter is provided with a movable member which receives a dynamic pressure by the flow of a fluid, a spiral spring biasing the movable member in a direction opposite to the dynamic pressure created by the flow of the fluid and a potentiometer with a slider connected to the movable member. The movable member is displaced an amount which corresponds to the amount of dynamic pressure created thereon and an analog voltage corresponding to the displacement of the movable member is obtained from the potentiometer. In this type of flow meter, it is desirable that the thin membrane resistance of the potentiometer be highly resistant against abrasion, the level of the output voltage for the position of the slider be stable, and furthermore, the looseness in the connection mechanism between the movable member and the slider be small and the contact between the slider and the membrane resistance also be stable even against vibration and shock.
However, contact between the slider and the membrane resistance in the potentiometer is of pressure contact. Consequently, over a period of time, an unstable output pressure will be caused relative to the dynamic pressure by the flow of fluid due to abrasion vibration and other causes.